Double brush holder



Nov. 21, 1933- J. L. BURNHAM 1,936,422

DOUBLE BRUSH HOLDER Filed Sept. 24, 1931 Inventor: Joseph L. Burnha'm,

b M M His Attorney Patented Nov. 21, 1933 PATENT OFFICE DOUBLE BRUSH HOLDER Joseph L. Burnham,

' to General Electric Company,

New York Schenectady, N. Y., assignor a corporation of Application September 24, 1931 Serial No. 564,879

5 Claims.

My invention relates to double brush holders for electrical maclnnes, and more particularly to double brush holders wherein the two brushes act as a single brush of the machine on which 5 it is used. 1 I

It has been proposed in electrical machines, in which the usual single brush has been replaced by two smaller brushes, to provide a double brush holder having separate springs cooperating with 1 each of the brushes to force them against the current collecting device. With this arrangement it is troublesome to obtain an equalization of brush pressures on the current collecting device because it is necessary to adjust the tension 1.5 of each spring separately.

An object of myinvention is to provide an improved double brush holder of this character wherein the pressures exerted by the brushes on a current collecting device are automatically go equalized. I accomplish this by providing a simplified double brush holder guiding two brushes in tandem and having an arrangement including a single spring cooperating with the brushes for .substantially equalizing the pressures exerted by 25 the brushes on a current collecting device.

Further objects and advantages of my invention will become apparent as the following description proceeds, and the features of novelty which characterize my invention will be pointed out with 0 particularity in the claims annexed to and forming a part of this specification.

In the drawing, Fig. 1 is a side elevation of .my improved double brush holder in its rela .tion to a current collecting device of an electrical machine; Fig. 2 is a longitudinal sectional view of the structure shown in Fig. 1; Fig. 3 is a top plan view of the structure illustrated in Fig. '1; and Fig. 4 is a transverse section taken on line 4-4 of Fig. 1.

In the drawing I have shown a pair of brushes 1 and 2 of equal width arranged in tandem and acting together as a single brush of an electrical machine, and which are supported in contact with a current collecting device 3 thereof by my 45 improved brush holder. These brushes may be connected in the circuit of the machine in any suitable manner. The brush holder comprises a :body 4 having a guideway 5 for the brushes, and spring actuated arms 6 and 7 in vertical align- 50 ment for urging the brushes against the current collecting device. Although I have shown the brushes contacting with each other, they may be separated by a partition or spacing plate in the v guideway so as to eliminate friction between 55 them.

As shown in Fig. 4, arms 6 and 7 are pivotally secured to the body 4 of the brush holder by riveting them to portions 8 and 9 respectively of angle plates 10 and 11, which are secured to hubs 12 brackets 15 extending upwardly on each side of the body 4. The outer end of the lower arm 6 is made U-shaped at 6' so that the portion 16 of the arm can extend downwardly and rest on the top of the brush 1 within the guideway 5. The upper arm 7 is provided with rectangular opening 18 to permit the U-shaped portion 6' of the lower arm 6 to extend therethrough, and the end thereof is bent as indicated at 19, so that the portion 20 can extend downwardly in the guideway. 5 and rest on top of the brush 2. By this arrangement of the pivotal connections a symmetrical simplified arrangement of the arms 6 and '7 is provided with the arms in vertical alignment, and the opening 18 in the upper arm '1 allows either of the arms to swing downwardly without interfering with the other as the brushes 1 and 2 are worn away.

A substantially equalized pressure of the brushes is automatically maintained by a linkage mechanism connecting the arms 6 and 7. This linkage mechanism comprises a toggle having a pair of spaced parallel links 21 pivotally connected at the upper ends thereof to a pin 22, which extends through a looped end of a projection, or lip 23, extending downwardly from the inner edge of the opening 18 in the upper arm '7. The lower ends of the links 21 are pivotally connected by a pin 24 to a link 25, which is pivotally connected at the other end to the lower arm 6 by a pin 26 secured to upwardly extending projections 2'7 on each side of the arm 6. Force is transmitted to the arms 5 and '7 through this linkage by a single helical spring 28 surrounding the hubs l2 and 13. One end 29 of the spring 28 engages the pivoted connection at 24 and the other end 30 thereof extends radially from the axis of the helix, and is hooked in notches 31 formed on the periphery of an arcuate plate 32 secured inside of one of the brackets 15. The end 30 of the spring can be shifted from one notch to another to adjust the spring pressure.

The desired equal pressures exerted by the brushes 1 and 2 on the current collecting device 3 is obtained, in the above described construction, by the single adjustment of the spring 28. The force of the spring 28 is transmitted to the linkage by the end 29 thereof engaging the pivotal connection at 24, and components of this force are transmitted to the arms 6 and '7 through the and 13 arranged on a pin 14 secured in I links 21 and 25. By properly proportioning the length and angular relation of the links 21 and 25, these component forces are made such that the force of the arms on the brushes will equalize 5 the pressure exerted by the brushes on the current collecting device 3, and maintain the pressure equalized as the brushes are shortened due to wear. If the brushes are of unequal widths, or the friction between them is excessive, the links 21 and 25 are proportioned so that the arms 6 and 7 will exert a predetermined ratio of pressures required to equalize the pressure per unit of contact area exerted by the brushes on the current collecting device. The brush pressures may vary slightly when one of the brushes is badly worn and the other is new, due to the angular displacement of the arms 6 and '7, but this variation in pressure Will be small and no greater than the variation in pressure exerted by a single brush as it becomes worn.

Modifications of the form of my invention which I have described will occur to those skilled in the art, so that I desire my invention not to be limited to the particular arrangement set forth, and I intend in the following claims to cover all modifications thereof which do not depart from the spirit and scope of my invention.

What I claim as new and desire to secure by Letters Patent of the United States is:-

1. A double brush holder including guide means for two brushes in tandem, a pivoted arm acting on one of said brushes, another pivoted arm acting on the other of said brushes and movable independently of said first-mentioned arm, a spring, and means including a linkage mechanism connecting said arms for transmitting force from said spring to said arms, and for substantially equalizing the pressure exerted by the brushes on a current collecting device.

2. A double brush holder comprising a body and means for guiding two brushes in tandem, a pair of arms pivotally supported on said body and arranged in vertical alignment, one of said arms having an opening for permitting a portion of said other arm to extend therethrough, each of said arms acting on one of the brushes, a spring, and means including a linkage mechanism connecting said arms for transmitting force from said spring to said arms and for substantial- 1y equalizing the pressure exerted by the brushes on a current collecting device.

3. A double brush holder comprising a body and means for guiding two brushes in tandem, a transverse pin supported on said body, a pair of arms pivotally supported on said pin and arranged in vertical alignment, one of said arms having an opening for permitting a portion of said other arm to extend therethrough, each of said arms acting on one of the brushes, a helical spring surrounding said pin, and means including a toggle mechanism connecting said arms for transmitting force from said spring to said arms and for substantially equalizing the pressure exerted by the brushes on a current collecting device.

4. A double brush holder comprising a body and means for guiding two brushes in tandem, a separate arm for each of said brushes, each of said arms being pivotally supported on said body for movement with respect to each other and arranged in vertical alignment, one of said arms having an opening for permitting a portion of said other arm to extend therethrough, and means for urging said arms against the brushes.

5. A double brush holder comprising a body and means for guiding two brushes in tandem. a transverse pin supported on said body, a pair of separate arms pivotally supported on said pin for movement with respect to each other and arranged in vertical alignment, one of said arms having a longitudinal opening for permitting a portion of said other arm to extend therethrough, and means for urging said arms against the brushes.

JOSEPH L. BURNHAM. 

